Tell Parents about 1 Bad Grade?

I got my progress repoprt today and i got a C+. It was because my teacher she didnt add the midterm that i got a 70 on onto our report cards. I have a vacation in 10 days and im missing a whole week of school and I dont want them to think that I can't handle it. I just did bad on part 2 of the test. I know that its just a progress report but its my lowest grade this year! I dont want to seem like a slacker to them and I studied really hard on for my midterm! I also know that progress reports arnt final so ANYTHING WILL HELP and no negative comments